Author: John Mulindi
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What is a Microsyn Transducer?
This is a variable-reluctance transducer used to detect small motions, giving output signals as low as 0.01° of changes in angles. The figure below shows an example of Microsyn: In the Microsyn transducer above, the coils are connected in such a way that at the null position of the rotary element, the voltages in coils…
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Steam-heated Reboiler Control System
When steam-heated reboilers are used in distillation columns and the heating medium is steam, a flow control loop for the steam will typically be incorporated. The control valve can then be placed either in the steam or condensate line. Steam pressure compensation is always recommended in these cases, and the controls are illustrated in the…
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Basic Features of Sercos Automation Bus
Sercos is a short form for serial real-time communication system; a digital automation bus that interconnects motion controls, drives, I/O, sensors, and auxiliary devices such as cameras and weighing stations. Sercos is an open controller-to-intelligent digital device interface, designed for high-speed serial communication of standardized closed loop data in real time (RT). Sercos I and…
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Installation Considerations of an Orifice Plate Flow Sensor
If a constriction is placed in a pipe as shown in figure 1 below, the flow must be higher through the restriction to maintain mass flow at all points. Since the mass flow must be equal at all points, the flow velocity must increase in the region of A2. As there is no net gain…
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Direct-on-line (DOL) Starter
Let’s consider an illustration of a typical three-phase direct-on-line (DOL) starter below: When the start button is pressed, the 415V contactor coil is energized, the main and auxiliary contacts close, and the motor starts. The auxiliary contact in parallel with the start button holds the coil on. Overload or overcurrent protection is provided by either…
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How cycloconverter is used as a direct frequency converter
The cycloconverter provides direct ac to ac transformation with control over both the output voltage magnitude and output frequency. It employs phase-angle-controlled bridges to synthesize voltages. The most common form is the three-phase to three-phase converter illustrated below: Each output needs two three-phase thyristor bridges. One bridge is used to synthesize positive voltages at the…
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Furnace Control System for a Rapidly Changing Demand
Let’s consider the figure below: In the system above, the output of temperature controller TC represents the process demand, and this signal is applied as one of the inputs, each to a high (>) and a low (<) signal selector block (module). The second input to the high (>) selector is obtained from the measurement…
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Basic Features of a Hartley Oscillator
The primary LC oscillator circuit does not have the option of controlling the amplitude of the oscillations. A weak electromagnetic coupling between first inductive coil L and second inductive coil L2 results in insufficient feedback and the oscillations would eventually die away to zero. Equally, a strong feedback causes the oscillations to increase in amplitude…
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Industrial Process Temperature Control System
Let’s consider the industrial process control system shown below: The requirement is to control the temperature ϴ in the tank. The voltage r, obtained from a potentiometer, is calibrated in terms of the desired temperature ϴc. This voltage represents the input quantity to the feedback control system. The actual temperature ϴ, the output quantity, is…
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What is a Microprocessor Clock?
The CPU clock dictates how fast the processor can process the data, and a microprocessor having a clock speed of 3 MHz means that it can process data internally 3 million times a second at every clock cycle. The crystal quartz oscillator is the most appropriate frequency determining device in virtually all microprocessors, microcontrollers, PICs…